Septic shock and the formation of pulmonary edema were studied in 19 baboons. Four animals served as controls. Four were subjected to deep septic shock by infusion of liveE. coliand then deliberately killed while in deep shock. Four were subjected to septic shock, resuscitated with Ringer's lactate (RL), and then killed 1½ hours after resuscitation was started. Seven were subjected to shock and resuscitation attempted with Plasmanate (PL).Resuscitation with RL was successful for 1½ hours in all four RL-animals. Resuscitation with PL was successful for 1½ hours in three of the 7 PL-animals. There was an increased tendency for albumin to extravasate into the interstitium of the lungs after resuscitation. The amount of pulmonary edema, measured by both the thermodye technique and by analysis of post-mortem lung composition, was the same in animals resuscitated with RL and PL. Administration of pure colloid offers no protection to the lungs in resuscitating patients from septic shock.